The invention relates to a braking apparatus for a vehicle.
One such braking apparatus is known from German Patent Disclosure DE 42 29 042 A1, FIG. 3. It has an electric motor, which via a gear-wheel gear rotatingly drives a spindle of a spindle drive that converts the rotary drive motion into a linear motion to press a brake lining against a brake disk as the brake body. The known braking apparatus also has an emergency actuating device, with which the braking apparatus can be actuated if its electric motor fails. The known braking apparatus has the disadvantage of having no capability for readjusting an air clearance between the brake lining and brake disk with increasing brake lining wear. As a consequence, the actuation distance and thus also the time that elapses from the time braking is initiated until the brake engages become longer as brake lining wear increases. Another disadvantage of the known braking apparatus is that because of the design of its emergency actuating device, it cannot be released if its electric motor or the power supply thereof fails when the brake is actuated.
From European Patent Disclosure EP 0 246 770 A3, a brake actuating apparatus for a railroad brake is known. It has a first electric motor, which drives a first spindle drive, whose spindle is intended to press a brake shoe against a railroad wheel. The first electric motor with the first spindle drive is used to overcome the air clearance. The known brake actuating apparatus also has a second electric motor for driving a second spindle drive, whose spindle nut, with a long lever arm, engages a single-armed lever that is supported in a manner fixed to the frame. With the short lever arm, the lever engages the first spindle drive, so that the entire first spindle drive can be displaced with great force via the lever. This displacement motion is used to bring to bear a braking force. The known brake actuating apparatus has the disadvantage that it is not embodied for readjusting the air clearance. It has the further disadvantage that if its first electric motor fails, the air clearance can no longer be overcome, and hence no further braking action is attainable. Another disadvantage of the known brake actuating apparatus is that if its second electric motor fails, only minimal braking force can then be brought to bear with the first electric motor, and that it can be released with the first electric motor only if this first electric motor is adequately large.